Barrel re-exports DateTimePickerProps from the optional peer @mui/x-date-pickers, so the type is any for consumers who skip it #1749

Current Behavior

dist/index.d.ts re-exports DateTimePickerProps from @mui/x-date-pickers/DateTimePicker:

import { DateTimePickerProps } from '@mui/x-date-pickers/DateTimePicker';
export { DateTimePickerProps } from '@mui/x-date-pickers/DateTimePicker';

@mui/x-date-pickers is declared optional under peerDependenciesMeta, so a consumer is
entitled to skip it. When they do, that reference does not resolve and the type quietly collapses:

• skipLibCheck: false -> TS2307: Cannot find module '@mui/x-date-pickers/DateTimePicker',
  pointing at sistent's own .d.ts rather than at the package actually missing;
• skipLibCheck: true (the common default) -> DateTimePickerProps silently becomes any.

Reproduced against a clean consumer with the optional peer absent - this probe compiles, which
it only can if the type degraded to any:

import type { DateTimePickerProps } from '@sistent/sistent';
type IsAny<T> = 0 extends (1 & T) ? true : false;
export const p: IsAny<DateTimePickerProps> = true;

Expected Behavior

Either the type does not appear in the barrel's public surface at all, or it resolves for every
consumer. A public type must not depend on a package the consumer was explicitly told is optional.

Context

This is the declaration-side twin of the optional-peer rule already documented in AGENTS.md
("The barrel must not require an optional peer"). The two fail in opposite directions: that one is
broken by a runtime import, this one by a type re-export - and import type being erased at
runtime is exactly why the existing runtime guard cannot see it.

DateTimePicker itself is correct here: it defers the runtime import via React.lazy
(src/base/DateTimePicker/DateTimePicker.tsx), which is the documented fix for the runtime half.
Only the type re-export is left over.

Discovered while fixing the same class of defect for @meshery/schemas, whose Key type was
degrading to any the same way. That fix landed with a guard,
src/__testing__/publishedTypeSurfaceDependencies.test.ts, which asserts that every external
package named by the built dist/index.d.ts is a real dependency or peerDependency.
@mui/x-date-pickers is currently exempted on the record in that guard's optional-peer
exemption list, pointing at this issue - so the guard stays honest about the hole instead of
hiding it.

Suggested fix

Preferred: stop re-exporting DateTimePickerProps from the root barrel, so the optional peer stops
being part of the published type surface.

Alternatives considered and not chosen:

• Promote @mui/x-date-pickers to a required peer - contradicts the optional-peer contract and the
  direction of Barrel import still requires the optional peer date-fns (UniversalFilter), breaking clean-install consumers #1735.
• Leave it exempted permanently - keeps a public type that is any for anyone who took the package
  at its word that the peer is optional.

Once resolved, delete the @mui/x-date-pickers entry from OPTIONAL_PEERS_ON_THE_RECORD in
src/__testing__/publishedTypeSurfaceDependencies.test.ts; the guard asserts each exemption is
still needed, so a stale entry fails the test rather than lingering.